8
5. Remove jumper wires and allow two minutes for the
safety heater to cool off.
6. Test running circuit by jumpering out T1 and T2 and
reset the primary control. The burner will come on.
7. Immediately jumper F1 and F2 to bypass the cad cell.
The burner should run continuously after 45 seconds
with the cad cell safety circuit by-passed.
8. Shut off power to the unit, remove all jumpers, and then
reconnect the thermostat and cad cell.
9. If any one of these test fails, replace the primary control.
Removing the Primary Control
1. Shut off power to the unit.
2. Open ignition transformer by removing 2 5/16" screws.
3. Remove the black, white and orange wires leading from
the primary control.
4. Remove cad cell wires from F1 and F2, and remove
thermostat wires from T1 and T2.
5. Loosen 2, 1/4" screws and remove primary control.
6. To replace, reverse steps 1-5.
Testing Cad Cell
The cad cell is a light sensing resistor. Its function is to cut
power to the burner motor in the event the electrodes fail to
establish flame.
To check the CAD cell start the burner and unhook both cad
cell leads from the FF terminals on the primary control. After
the burner lights jump the FF terminals to keep the burner
running. Measure the ohms resistance across the cad cell
lead as it views the flame. This should be 1,600 ohms or less.
A preferred reading is 300-1000 ohms. Next, with the meter
still connected to the cad cell leads, turn the burner OFF. The
dark condition should give a reading of 100,000 ohms or
infinity. If the reading is lower, let the refractory cool down or
look for stray light that might be entering the burner through
the air inlet, or around the transformer base plate. If the cad
cell is not performing within these guidelines, replace it.
Removing the Cad Cell
(See Figures 17 and 18)
1. Shut off power to the unit.
2. Remove wires from primary control.
3. Open ignition transformer.
4. Turn cad cell 1/2 turn in retainer and lift out.
5. To replace, reverse steps 1-4.
Testing Ignition Transformer (See Figure 20)
Figure 17
Figure 18
WARNING
In testing the ignition transformer extreme
caution should be exercised because 10,000 to
14,000 volts are present.
!
Figure 19
Figure 20
The most common field test of the ignition transformation
spark is using a service test cord connected to the primary
winding wiring and an INSULATED screw driver. The tests
should indicate an arc:
1. 1/2" long ARC from the terminal post to the casing.
